Trimming Help

[Bob Pastorello]

Courtesy of Buddy, I've placed (with his permission) his summary of the "trimming" issues.  Probably many of you share my view that his summary was one of the most on-target, concise statements I've read about trimming in a VERY long time, if ever!!!  Posted here for your reference:
http://www.rcaerobats.net/trim_chart.htm

Thanks, Buddy!

Bob Pastorello, Oklahoma
NSRCA 199, AMA 46373
rcaerobob at cox.net
www.rcaerobats.net


  ----- Original Message ----- 
  From: BUDDYonRC at aol.com 
  To: discussion at nsrca.org 
  Sent: Tuesday, March 30, 2004 1:08 PM
  Subject: Re: Trimming Help


  Paul
  I am no aerodynamics expert, but I have learned some basic's over the years that work for me.
  1. The wing must have a positive angle of attack to create lift.
  2. the stabilizer and elevators steer the pitch attitude of the airplane resulting in more or less lift.
  3. Balance can change the angle of attack which will change the pitch attitude.
  4. Aileron's up or down will change the pitch attitude .
  5. Up or down thrust will change the pitch attitude.
  Therefore:
  A. Increasing the positive wing incidence will cause the airplane to climb, which will require down trim to achieve level flight.
  B. Likewise adding tail weight will cause the airplane to climb and require down trim to achieve level flight.
  C. Added weight does not alter the vertical down line BUT elevator trim added to maintain level flight because of the added weight will effect the down line. Tail weight will require down trim which will steer the airplane more to the belly in a down line, and added nose weight will require up trim which will steer the airplane to the canopy.
  D. In the vertical up line elevator trim and the engine thrust line will effect the vertical and/or yaw direction   
  All of the above will effect the knife edge flight of the model.
  Combinations of adjustments to any or all of the above trim items done at the same time will leave you confused and frustrated.
  Most models will require some mixing to achieve near perfect lines in all flight attitudes in order to minimize / eliminate control inputs by the pilot to maintain a perfect course.
  I have yet to see the perfect airplane should such an animal exist, but I keep looking and building since I truly believe that nothing is impossible.
  When trimming an airplane make a written log of every change no matter how small so you don't have to start over when changes are not correct.
  Buddy 
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